EFSA assesses the public health risk of seeds and sprouted seeds
15 November 2011
The European Food Safety Authority (EFSA) has evaluated the public health risk of Shiga-toxin producing Escherichia coli (STEC) and other pathogenic bacteria that may contaminate seeds intended for sprouting and sprouted seeds (sprouts, shoots and cress). Recognising that sprouted seeds are generally consumed raw or minimally processed, the Panel on Biological Hazards (BIOHAZ Panel) concludes that sprouted seeds are ready-to-eat foods with food safety concerns because certain pathogenic bacteria can contaminate seeds and grow during sprouting. Furthermore, preventing initial contamination during production, storage and distribution of seeds is of the foremost importance, as sprouted seeds have the potential to cause large food-borne outbreaks. Operators producing sprouted seeds should strive to implement additional food safety management measures across the whole sprout production chain. Stakeholders at all parts of the production chain and consumers, including also those practising home-sprouting, should be informed of the food safety risk posed by sprouted seeds.
The European Commission requested a risk assessment of seeds and sprouted seeds intended for human consumption following the most recent outbreaks in Germany and France in spring and summer 2011. In its opinion, the BIOHAZ Panel noted that large outbreaks associated with consumption of contaminated sprouts have previously been reported in the EU and worldwide. Sprout-associated outbreaks are most commonly caused by Salmonella and pathogenic E. coli (including STEC). Very low levels of the bacteria - as little as 4 bacteria/kg - in seeds intended for sprouting have been sufficient to cause outbreaks.
The Panel concludes that sprouted seeds pose specific microbial food safety concerns and that there are several risk factors for contamination affecting the entire sprouted seed production chain. Pathogenic bacteria can contaminate the seeds intended for sprouting during production, storage and distribution through, for example, contaminated irrigation water and soil particles. The high temperature and humidity needed for the germination and sprouting of seeds are also favourable conditions for pathogenic bacteria to further grow and spread. Consumption of raw or minimally processed sprouted seeds pose additional food safety concerns. EFSA’s risk assessment focused on seeds and sprouts, as there is limited scientific information available on shoots and cress.
EFSA’s BIOHAZ Panel considers sprouted seeds as ready-to-eat foods and therefore recommends that general EU food safety hygiene rules should be applied across the whole chain from seed production to the final sprouted product. The Panel concludes that preventing initial contamination of seeds intended for sprouting is of particular importance, as there are currently no methods to ensure elimination of pathogens in all types of seeds used for sprouting. The Panel notes that the control of a sprout-associated outbreak is challenging as seed lots can be widely distributed and therefore difficult to trace.
Panel recommends additional safety measures for the sprouted seed production chain
As for other ready-to-eat food products, the BIOHAZ Panel recommends that additional food safety management measures should be put in place along the whole chain from seed production to the final sprouted product.
Microbiological criteria should be an additional step in managing food safety in the sprouted seed production chain. However, the Panel recognises the difficulties of detecting contamination with testing, and that reliable results would require the analysis of large samples and/or different sampling strategies. In addition, due to the short shelf life of sprouted seeds, rapid methods for detecting pathogenic bacteria are important to obtain timely results.
Given the complex nature of the sprouted seed production chain, the Panel considers different approaches and makes a variety of suggestions for mitigation options throughout the production chain that could assist risk managers in setting policies and making decisions to protect consumers in the European Union.
- Scientific Opinion on the risk posed by Shiga toxin-producing Escherichia coli (STEC) and other pathogenic bacteria in seeds and sprouted seeds
Notes to editors:
Sprouted seeds intended for human consumption are obtained from the germination of seeds and are most commonly eaten as:
- Sprouts are developed in water and are collected before the development of leaves. The final product still contains the seed.
- Shoots are developed in water to produce a green shoot with very young leaves and/or embryonic leaves (cotyledons). The shoots are harvested and the final product does not include the seed (teguments) and roots.
- Cress are developed in soil or in substrate to produce a green shoot with very young leaves and/or embryonic leaves. Cress are usually sold as entire plants in substrate or soil.
 Some E. coli strains are able to produce toxins which can be harmful to humans. These strains are called STEC/VTEC (shiga toxin or verotoxin-producing E. coli) or EHEC (enterohaemorrhagic E. coli). In the EU and as reflected in EFSA’s work on zoonoses, shiga toxin-producing Escherichia coli is referred to as VTEC (verotoxin-producing E. coli). However, the term STEC is used for this opinion as it is in line with terminology used by WHO and other organisations to refer to the German outbreak in 2011.
 Such as Hazard Analysis and Critical Control Point (HACCP) principles, Good Hygiene Practices (GHP), Good Agricultural Practices (GAP) and Good Manufacturing Practices (GMP).
 Other bacterial pathogens (e.g. Bacillus cereus, Listeria monocytogenes and Yersinia enterocolitica) have also been implicated in sprout-associated outbreaks, but very rarely.
 Suggested mitigation options include but are not limited to: identifying seed crops intended for sprout production before planting; safe use of fertilizers and irrigation water; minimizing contamination of seeds with soil during harvest and preventing mechanical damage of seeds; ensuring that workers harvesting and handling seeds follow hygiene and health requirements; ensuring that seeds are transported, processed and stored under conditions which will minimize the potential for microbial contamination; removing damaged seeds; and improving traceability and minimizing mixing of seed lots.